The present invention relates to a communication system comprising a distributed terminal designed to offer services to a number of users based on a single subscription to a mobile radio network, and a method for supervising communication that can be used in such a system.
Distributed mobile radio terminals are known. Such a terminal model has been adopted by the 3GPP organization (see technical report 3G TR 27.901, version 3.0.0, Jan. 2000). In particular, the GPRS (General Packet Radio Service) technology, which is an extension of the GSM (Global System for Mobile communications) system standardized by the ETSI (European Telecommunications Standards Institute), can be used to separate two entities within a terminal:                a mobile termination, or MT, which is responsible for radio transmission and reception with respect to the GPRS network according to a conventional GSM-type air interface, and        a terminal equipment, or TE, which incorporates the highest level protocol layers, typically from the transport layer to the application layer, based on a layered OSI (Open System Interconnect) representation model.        
The communication between the MT and the TE is normally conducted via a non-specific point-to-point or point-to-multipoint link. Thus, a terminal equipped with GPRS technology can interchange data with a GPRS network which may be interconnected with a network containing application servers, by exploiting the application and presentation capabilities of the TE and the radio transmission offered by the MT.
By way of illustration of this technology and its applications, it is worth remembering that numerous mobile phones currently incorporate a modem and have a port which can be used to connect them to a peripheral device, such as a personal digital assistant. In this case, a person having taken out a subscription with an operator having a mobile radio network can use his or her personal assistant as terminal equipment (TE), for example to consult an Internet data site, whereas the mobile phone (MT in this case) will act as a relay for the Internet protocol (IP) data for which it will adapt the format for interchanging the data, over a radio channel, with the mobile radio network, itself connected to the Internet in this example.
The UMTS (Universal Mobile Telecommunication System) technology, standardized by the 3GPP, can be used to obtain the same separation between MT and TE. A UMTS distributed terminal can therefore in the same way interchange data with a UMTS network.
Moreover, there are mobile radio terminals that can support several simultaneous communications.
The abovementioned GPRS system can be used to open, for the same user, a number of communication sessions, called PDP (Packet Data Protocol) contexts, for the purpose of packet mode data interchanges with the network. Because of this functionality, a user can theoretically surf the Internet in WAP (Wireless Application Protocol) mode on his or her GPRS mobile phone and access a website on his or her computer connected to his or her mobile phone, via the activation of two PDP contexts.
The UMTS system provides the same capability and in addition has a multicall functionality enabling a plurality of speech calls to be set up, for a particular user, using a circuit mode transmission, each speech call being carried by a dedicated radio channel. A general description of this function can be found in the technical specification TS 22.135, version 4.0.0, published by the 3GPP in Mar. 2000. Such multicall systems are described for example in US-A-2002/013150 and EP-A-0 971 525.
However, the use of a distributed terminal as described previously is linked to the concept of mobile radio network subscriber, because a user must have a subscription from which the network operator manages his or her profile and his or her calls (service access, call characteristics, usage billing, etc.). The subscription with the operator is in practice embodied, in a GSM or UMTS type cellular system, by a subscriber identity module (SIM) belonging to the MT. If two people want to use the services offered by a mobile operator, for example using two TEs linked to the same MT, the network operator can no longer distinguish between the two users.
An object of the present invention is to allow independent supervision of the various users of a mobile radio network, in a shared network subscription model.
Another object of the present invention is to allow an independent use of the services offered by a mobile operator for different users from a shared network subscription.